form_fieldtype(3x) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | SEE ALSO | NOTES | PORTABILITY | AUTHORS | COLOPHON

form_fieldtype(3X)                                    form_fieldtype(3X)

NAME         top

       form_fieldtype - define validation-field types

SYNOPSIS         top

       #include <form.h>

       FIELDTYPE *new_fieldtype(
           bool (* const field_check)(FIELD *, const void *),
           bool (* const char_check)(int, const void *));
       int free_fieldtype(FIELDTYPE *fieldtype);

       int set_fieldtype_arg(
           FIELDTYPE *fieldtype,
           void *(* const make_arg)(va_list *),
           void *(* const copy_arg)(const void *),
           void  (* const free_arg)(void *));
       int set_fieldtype_choice(
           FIELDTYPE *fieldtype,
           bool (* const next_choice)(FIELD *, const void *),
           bool (* const prev_choice)(FIELD *, const void *));

       FIELDTYPE *link_fieldtype(FIELDTYPE *type1,
                                 FIELDTYPE *type2);

DESCRIPTION         top

   new_fieldtype
       The function new_fieldtype creates a new field type usable for
       data validation.  Its parameters are function pointers:

       field_check
            This function checks the validity of an entered data string
            whenever the user attempts to leave a field.  It has two
            arguments:

            •   The (FIELD *) argument is passed in so the validation
                predicate can see the field's buffer, sizes and other
                attributes.

            •   The second argument is an argument-block structure,
                about which more below.

       char_check
            This function validates input characters as they are
            entered.  The form library passes it the character to be
            checked and a pointer to an argument-block structure.

   free_fieldtype
       The free_fieldtype function frees the space allocated for a given
       validation type by new_fieldtype.

   set_fieldtype_arg
       The function set_fieldtype_arg associates three storage-
       management functions with a field type:

       make_arg
            This function is automatically applied to the list of
            arguments you give set_field_type when attaching validation
            to a field.  It stores the arguments in an allocated
            argument-block object which is used when validating input.

       copy_arg
            This function may be used by applications to copy argument-
            blocks.

       free_arg
            Frees an argument-block structure.

       You must supply the make_arg function.  The other two are
       optional: you may supply NULL for them.  In this case, the form
       library assumes that make_arg does not allocate memory but simply
       loads the argument into a single scalar value.

   set_fieldtype_choice
       The form driver requests REQ_NEXT_CHOICE and REQ_PREV_CHOICE
       assume that the possible values of a field form an ordered set,
       and provide the forms user with a way to move through the set.

       The set_fieldtype_choice function allows forms programmers to
       define successor and predecessor functions for the field type.
       These functions take the field pointer and an argument-block
       structure as arguments.

   link_fieldtype
       The function link_fieldtype creates a new field type from the two
       given types.  They are connected by an logical 'OR'.

RETURN VALUE         top

       The pointer-valued routines return NULL on error.  They set errno
       according to their success:

       E_OK The routine succeeded.

       E_BAD_ARGUMENT
            Routine detected an incorrect or out-of-range argument.

       E_SYSTEM_ERROR
            System error occurred, e.g., malloc failure.

       The integer-valued routines return one of the following codes on
       error:

       E_OK The routine succeeded.

       E_BAD_ARGUMENT
            Routine detected an incorrect or out-of-range argument.

       E_CONNECTED
            The field is already connected to a form.

       E_CURRENT
            The field is the current field.

       E_SYSTEM_ERROR
            System error occurred (see errno(3)).

SEE ALSO         top

       curses(3X), form(3X), form_field_validation(3X).

NOTES         top

       The header file <form.h> automatically includes the header file
       <curses.h>.

PORTABILITY         top

       These routines emulate the System V forms library.  They were not
       supported on Version 7 or BSD versions.

AUTHORS         top

       Juergen Pfeifer.  Manual pages and adaptation for new curses by
       Eric S. Raymond.

COLOPHON         top

       This page is part of the ncurses (new curses) project.
       Information about the project can be found at 
       ⟨https://www.gnu.org/software/ncurses/ncurses.html⟩.  If you have
       a bug report for this manual page, send it to
       bug-ncurses-request@gnu.org.  This page was obtained from the
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       ⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2021-08-27.  (At
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                                                      form_fieldtype(3X)